The incineration of refuse to form combustible gases which may be usefully burned or otherwise employed is disclosed in U.S. Pat. No. 1,598,380, issued in 1926.
In the 1970's, attention was directed to the conversion of scrap rubber, especially scrap tires, to produce fuel and other useful by-products. Examples of processes for burning or the pyrolysis of rubbers and specific equipment for carrying out the processes are disclosed in U.S. Pat. Nos. 3,890,141; 3,926,582 and 3,946,680. The process disclosed in U.S. Pat. No. 3,890,141 first heats the solid waste in contact with a hydrocarbon liquid to convert the solid waste to a fluid. In the process and apparatus disclosed in U.S. Pat. No. 3,926,582, the solid waste material is introduced to a substantially vertical pyrolysis chamber, having a vertical core member, which charges an oxygen-rich gas into the chamber at a plurality of vertically spaced points. The charging of the oxygen rich gas is controlled to maintain incomplete combustion of the waste organic component and form a combustible gas and an organic-free molten refractory material. The apparatus disclosed in U.S. Pat. No. 3,946,680 specifically utilizes, in each of the embodiments, a non-combustible particulate material, formed of steel, aluminum, ceramic material, etc., which provides a bed over which the meltable waste is burned. Either a grate provided with a shaker means or a travelling grate is disclosed.
Considerable attention has been directed to the furnace or pyrolyzing apparatus. Handling of the solid waste poses problems which have been solved in very different ways. U.S. Pat. No. 4,387,652 discloses a plurality of downwardly inclined screw conveyors disposed in troughs to handle the steel wire in the residue from the pyrolytic heating of tires. The apparatus disclosed in U.S. Pat. No. 4,401,513 utilizes a "tote bin" which is specifically designed to be introduced into the oven or furnace on rails. The apparatus disclosed in U.S. Pat. No. 4,452,154 provides a number of leakage-sealing dampers in a vertical furnace to cause the tires to descend progressively, causing the lower tires to undergo oxidative combustion, dry distilling the upper tires with the combustion gases, and collecting gaseous fuel and/or liquid fuel from the combustion and distillation. The thermal decomposition furnace for waste tires disclosed in U.S. Pat. Nos. 4,565,138 and 4,572,082 have a fluidized bed-forming section and below that section, a sealing bed-forming section having a smaller diameter than that of the fluidized bed-forming section. Refractory material is utilized in the fluidized bed and effectively seals the lower section.
The pyrolitic apparatus disclosed in U.S. Pat. Nos. 4,109,590 and 4,507,174 illustrate the extremes of the prior devices and methods used when utilizing air. The apparatus disclosed in U.S. Pat. No. 4,109,590 requires an air-starved hot moving grate carbonizer furnace and then further, a shaft furnace. In the pyrolytic apparatus disclosed in U.S. Pat. No. 4,507,174, it is disclosed that: "After the door is closed no additional air or oxygen is provided in the reaction chamber . . . "
The present invention overcomes the many disadvantages and problems of the prior patents by providing a structure which easily handles solid waste, such as old tires, and controls the pyrolysis when using air as the pyrolysis heating gas.